Move PyInstaller hook tests into sub-directory

Move PyInstaller hook test (test_freetype.py and conftest.py)
into tests sub-directory. This prevents the test from using
the local (source) version of `freetype` instead of the installed
one (which contains the shared library); this problem arises with
pytest's default `prepend` import mode due to the project's
structure (i.e., not using the `src/freetype` layout).

.github/workflows/ci.yml

@@ -118,4 +118,4 @@ jobs:
       run: |
         pip install pytest psutil pyinstaller>=4
         FREETYPEPY_BUNDLE_FT=yes PYTHON_ARCH=64 pip install .
-        pytest -v freetype/__pyinstaller
+        pytest -v freetype/__pyinstaller/tests

freetype/__pyinstaller/__init__.py

@@ -1,12 +1,12 @@
-from os.path import dirname
+import os
 
 
-HERE = dirname(__file__)
+HERE = os.path.dirname(__file__)
 
 
 def get_hook_dirs():
     return [HERE]
 
 
 def get_test_dirs():
-    return [HERE]
+    return [os.path.join(HERE, 'tests')]

setup.py

@@ -109,7 +109,7 @@ def build_extension(self, ext):
     author_email='[email protected]',
     url='https://github.com/rougier/freetype-py',
     python_requires=">=3.7",
-    packages=['freetype', 'freetype.ft_enums', 'freetype.__pyinstaller'],
+    packages=['freetype', 'freetype.ft_enums', 'freetype.__pyinstaller', 'freetype.__pyinstaller.tests'],
     ext_modules=ext_modules,
     zip_safe=False if ext_modules else True,
     cmdclass=cmdclass,